Abundance of the vector Aedes aegypti in urban and rural areas in Managua, Nicaragua

Abstract

BACKGROUND: Ae. aegypti is the primary vector of dengue, chikungunya, Zika, and yellow fever viruses, traditionally associated with urban environments. However, its presence and abundance in rural settings remain understudied. This study compares Ae. aegypti populations between rural and urban communities in Managua, Nicaragua, across different seasons over multiple years. METHODS: Entomological surveys were conducted in 500 randomly selected houses (250 rural, 250 urban) during the rainy and dry seasons of 2022 and 2023. Immature mosquitoes were collected from water-holding containers, and adult mosquitoes were sampled using aspirators. Stegomyia, pupal, and adult indices were calculated. Generalized linear mixed models (GLMM) and generalized additive mixed models (GAMM) were used to evaluate factors associated with pupal productivity and adult female abundance. RESULTS: Rural communities consistently exhibited higher immature and adult Ae. aegypti abundance than urban communities across most entomological indices. Rural households accounted for 74% of collected pupae and had 3.34 times higher pupal counts compared with urban households (95% CI: 2.17-5.15, p < 0.001). Barrels were the most productive container type in both settings, with uncovered barrels increasing pupal counts by 73% (IRR = 1.73, 95% CI: 1.63-1.82, p < 0.001). Total adult female abundance was significantly higher in rural communities compared to urban ones (IRR = 1.39, 95% CI = 1.13 - 1.72, p < 0.001). Rural households also exhibited 67% higher female rates per person than urban households (IRR = 1.67, 95% CI: 1.33-2.09). Nonlinear modeling revealed threshold-like dynamics between pupal counts and adult female abundance, with sharp increases in adult density once pupal abundance exceeded 50 pupae. CONCLUSION: We consistently observed that rural communities in Managua sustain significantly higher Ae. aegypti populations than urban ones. The identification of pupal thresholds linked to adult abundance highlights the importance of preventing containers from reaching high productivity levels. Overall, these findings challenge the perception of Ae. aegypti as predominantly urban and underscore the need for integrated rural-urban surveillance and context-specific vector control strategies.